Adjustable limit for the advance of an ignition distributor

ABSTRACT

An ignition distributor wherein a drive plate is fixed to the distributor input shaft; a pair of centrifugal weights are pivotally connected to the drive plate and normally biased to the retard position: an advance plate is pivoted with respect to the distributor shaft with the pivoting movement controlled by the centrifugal movement of the weights, the advance plate being connected to the distributor cam which is fixed to the output shaft: a stop plate movable with respect to the advance plate is locatable in various positions with respect thereto, each position establishing a different maximum outward movement of the centrifugal weights.

Umted States Patent 11 1 1111 3,776,21 1

Droke et al. Dec. 4, 1973 [54] ADJUSTABLE LIMIT FOR THE ADVANCE 2,391,525 12/1945 Spengler 123/117 OF AN IGNITION DISTRIBUTOR 2,107,470 2/1938 Crawford.... 123/1465 1,896,714 2/1933 Mallory 123/117 [75] Inventors: Darr ll W- Dr k N p Donald 3,482,559 12/1969 Salomon 123 117 R. Ochampaugh, Bell; Andrew G. L05 Alamitos, all of Calif- Primary Examiner-Laurence M. Goodridge [73] Assignee: Cragar Industries, Inc., Compton, Assis'am Examiner l Cox Calif. AttrneyWarren T. Jessup et al.

[22] Filed: July 22, 1971 57 ABSTRACT [21] Appl. No.: 165,243 An ignition distributor wherein a drive plate is fixed to the distributor input shaft; a pair of centrifugal weights [52] Us Cl 123/146 A 123/117 R 123/146 5 R are pivotally connected to the drive plate and nor- [51 F02 6 F02 m4 mally biased to the retard position: an advance plate is [58] Fie'ld 125117 i 5 A pivoted with respect to the distributor shaft with the 123/146 4/25 1 pivoting movement controlled by the centrifugal movement of the weights, the advance plate being connected to the distributor cam which is fixed to the [56] References Cited output shaft: 2. stop plate movable with respect to the UNITED STATES PATENTS advance plate is locatable in various positions with re- 3,430,459 969 H l 1 spect thereto, each position establishing a different 2 1 maxinium outward movement of the centrifugal oge 3,196,224 7/1965 Tagliabue 200 22 2,677,946 5/1954 Purdy 123 117 5 Claims, 4 Drawing Figures l HI/I111 I l l 42 50 h I M 1 50 L I 1 I 1 I l l l/ PMENIEDBEE 4:915

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DARRELL W DROKE DONALD E. OCHAMPAUGH ANDREW G. KRUMM JESSUP 8 BEECHER A TTORNE 1 ADJUSTABLE LIMIT FOR THE ADVANCE OF AN IGNITION DISTRIBUTOR BACKGROUND OF THE INVENTION The field of this invention relates to internal combustion engines and more particularly to a means in the ignition distributor which limits the advanceof the firing of the engine.

A distributor can be defined as a rotary switch that directs the high voltage ignition current,'in the proper firing sequence, to the various cylinders of the internal combustion engine. In automotive practice the distrib utor usually contains apparatus for timing the ignition so that firing occurs when the piston is at the optimum position in the cycle. This apparatus includes a set of cam-operated contacts called breaker points, the opening of which triggers the ignition pulse. The timing of the breaker point opening is made earlier at high engine speeds by means of the centrifugal action of small weights that are driven by the distributor shaft. Timing is also varied with engine load, by the movement of a diaphragm exposed to the pressure in the engine intake manifold.

The advance of the timing is very important to efficient and smooth operation of the engine. As the operating speed of the engine increases, it is desirable to further advance the igniting spark. However, the igniting spark can be advanced an excessive amount. If the advance of the spark is not checked, at unusually high vehicle operating speeds, the spark will be advanced so far as to cause the engine to operate inefficiently.

To prevent the problem of excessive spark advance,

it is common to employ within the distributor of an engine a means to prevent the spark advancing beyond a predetermined amount. Centrifugal force responsive weights, which are caused to move radially outward as the velocity of the distributor shaft increases, is prevented from further outward movement upon reaching a predetermined amount of movement. In this way the advance of the spark is prevented permitted from exceeding a predetermined level. The primary reason for the limiting of the advance of the spark is to make the engine run more efficiently. To have the engine operate more efficiently howeve 1', power is usually sacrificed. In certain types of vehicles it is not desirable to sacrifice power, as for example, racing cars, drag racers and the like, and it is desirable for such types of vehicles to not permit the spark l be advanced as high as it would be advanced in the no-rnal passenger vehicle.

Additionally, different types of high performance ehicles need to have different levels of spark advance. For example, it may be desirable to advance the spark further in a drag racer than in a racer which is to be run over a long distance course. Also, it is not uncommon for the same engine to be used in different types ot racing. Additionally, the same engine may be transformed into a passenger type vehicle for a period of time. \s a result, it is desirable to be able to select various stopping points to limit the advance of the spark of the en- Heretofore, there have been known apparatuses to permit selective adjustment of the firing of the engine. However, such apparatuses have been quite complex in construction and as a result are quite costly to manufacture. Additionally, such previous apparatuses have necessitated the removal of a pin from one aperture and its relocation within another aperture to effect a change in the timing advance. Normally, such a removal and replacement of a pin is not readily accom' plished within the tight quarters of a distributor housing. Additionally, if the pin is accidentally dropped, it may be impossible to find it without taking the entire distributor apart.

SUMMARY OF THE INVENTION Basically, the apparatus of this invention is designed to be employed in conjunction with the conventional distributor apparatus. The conventional distributor apparatus includes an input (or distributor) shaft which is to be rotatably driven at varying speed by the engine crankshaft. A drive plate is fixedly connected to the input shaft within the distributor holising. A pair of weights are pivotally attached to the drive plate and located on either side of the distributor shaft. The weights are normally spring biased toward each other to the retard position of the timing advance. A pin is secured to each weight, with each pin cooperating in a respective slot formed in an advance plate. The slots formed in the advance plate are inclined, so that upon radially outward movement of the weights with respect to the distributor shaft, pivotal movement of the ad-' vance plate with respect to the distributor shaft will occur. The advance plate is fixedly secured to the output shaft (or the shaft upon which is located the distributor cam) which effects the opening and closing of the distributor breakingpoints. Specifically, the apparatus of this invention provides for the inclusion of a stop plate pivotally mounted on the distributor shaft and located between the weights and the advance plate. The stop plate includes at least one opening therein which coop erates with one of the pins extending from one of the weights. Along the width of the opening in the stop plate are located a plurality of different length slots which vary in radial distance with respect to the distributor shaft. The radially outermost end of each slot, upon being contacted by the pin connected to the weight, prevents the further radially outward move-. ment of the weight assembly, therelby limiting the spark advance. Pawl or tab means is secured to the radially outermost edge of the stop plate and is adapted to cooperate with notch means formed in the advance plate. The pawl means and notch means fixedly retain, in a particular established angular position, the stop plate relative to the advance plate.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an exploded perspective view of a conventional distributor within which is incorporated the apparatus of this invention;

FIG. 2 is a plan view of a portion of the distributor within which the apparatus of this invention is employed, taken along line 22 of FIG. 1;

FIG. 3 is a plan view of one form of the stop plate which is employed within this invention; and

FIG. 4 is a side view of the stop plate of FIG. 3 taken along line 4-4 of FIG. 3.

DETAILED DESCRIPTION OF THE SHOWN EMBODIMENT Referring particularly to the drawing there is shown in FIG. 1 a distributor which is designed to be employed in conjunction with an internal combustion engine (not shown). The crankshaft (not shown), which is the output shaft of the engine, effects rotation of the distributor shaft 12. It is to be understood that as the engine crankshaft varies in rotational velocity, so also does the distributor shaft 12. The distributor shaft 12 is rotatably supported by bearings (not shown) within the lower element 14 of the distributor housing. Within the distributor cap 16 are located a plurality of contact points (not shown), each of whichis connected through a conductor (not shown) to a spark plug. Each spark plug effects ignition of the compressed fuel/air mixture located within a cylinder of the engine.

A rotor 18 is adapted to cooperate with the contacts located within the distributor cap 16. The lower end of the rotor 18 passes through, and resides in, an opening 20 formed within the intermediate element 22 of the distributor housing. The distributor cap 16 comprises the upper element of the distributor housing. The lower end of the rotor 18 is fixedly positioned upon the output shaft 24. A cam 26 is integrally formed upon the output shaft 24. The cam 26 cooperates with followers 28 and 30 which are connected to their respective breaker point assemblies 32 and 34. The breaker point assemblies 32 and 34 are conventional and need not be described here in detail. Basically, each of the breaker point assemblies 32 and 34 include a set of points 36 and 38, respectively, which are openable and closable by means of the cam 26 via the followers 28 and 30. It is to be noted that the two breaker point assemblies 32 and 34 are here shown. Normally, two such breaker point assemblies are employed only in high performance type of vehicles. It is to be understood that the apparatus of this invention equally readily employed upon a more conventional distributor whichemploys the use of only one breaker point assembly.

The output shaft 24 is fixedly secured to an advance plate 40. Formed in one end of the advance plate 40 is a first set 42 of notches. Located on the opposite side of the advance plate 40' is a second set 44 of notches. The function of the notches 42 and 44 will be described further on in this specification. It is to be noted that both sets 42 and 44 comprise four of such notches. The number of the nothces is a matter of choice or design. It is further to be noted that, as shown in FIG. 2 of the drawing, the notches 42 are denoted by indicia of 8, 10, 12, and

Also formed within the advance plate 40 are slots 46 and 48, each inclined to the radius a predetermined amount. The reason for this inclination will become apparent further on in the description. Slot 46 is cooperable with a pin 50; slot 48 is cooperable with a pin 52. Pin 50 is fixedly secured upon a weight 54. Pin 52 is fixedly secured to a weight 56. One end of the weight 54 is pivotally connected through pivot pin 58 to a drive plate 60. Similarly, one end of the weight 56 is pivotally connected through a pivot pin 62 to the drive plate 60. The weights 54 and 56 are so located upon the drive plate that the pivot pins 58 and 60 are substantially 180 apart with respect to the distributor shaft 12. The. drive plate 60 surrounds the distributor shaft 12 and is fixedly connected thereto. Secured to the upper surface of the weight 54 are pins 64 and.66. Similarly, secured to the upper surface of the weight 56 are pins 68 and 70. A spring 72 is connected between the pins 66 and 68. Similarly, a spring 74 is connected between the pins 64 and 70. The function of the springs 72 and 74 is to tend to maintain the weights 54 and 56 in the retard position (nearest each other).

The operation of the weights 54 and 56, which is conventional, is as follows: The distributor shaft 12 effects rotation of the drive plate 60, which in turn effects rotation of the weights 54 and 56. As the centrifugal force increases, the weights 54 and 56 tend to move radially outward against the bias of springs 72 and 74. The amount of radially outward movement of the weights 54 and 56 is dependent upon the rotational velocity of the shaft 12. In other words, as the rotational velocity of the shaft 12 increases, the further outward is the amount of radial movement of the weights 54 and 56. As the weights 54 and 56 move outwardly, the pins 50 and 52, through their respective slots 46 and 48, effect pivotal movement of the advance plate 40 with respect to the distributor shaft 12. Since the output shaft 24 and the cam 26 are fixedly secured to the advance plate 40, pivotal movement of the output shaft 24 and the cam 26 also occurs with respect to the distributor shaft 12. As a result, the points 36 and 38 of the breaker point assemblies 32 and 34 are caused to open up a few degrees earlier (or in advance) due to the pivoting of the output shaft 24 with respect to the input shaft 12.

Located intermediate the advance plate 40 and the weight 54 is a stop plate 76. The stop plate 76 has a circular opening 78 formed therein residing around the input shaft 12. Also located in the stop plate 76 is an opening 80. Basically, the opening 80 is composed of a plurality of different length slots connected together side by side. It is to be noted that the end 82 of the slot comprises a series of recesses 84 formed on an angle. integrally secured to the radially outermost edge of the stop plate 76 tab or pawl 86.

With the stop plate 76 located so that opening 78 is circumjacent the input shaft 12 and with the stop plate 76 located between the advance plate 40 and the weight 54, the pin 50 passes through opening 80. With the tab or pawl 86 cooperating with the 8 notch 42 of the advance plate 40, the pin 50 is capable of coming into contact with that recess 84 which is the radially shortest distance from the distributor shaft 12. When such occurs further radial outward movement of the weights 54 and 56 is prevented. When this occurs, the rotation of the output shaft 24 with respect to the input shaft 12 has been approximately 8.

It is to be understood that the mechanic or operator may cause the pawl 86 to cooperate with any of the notches 42 such as the 10 notch, 12 notch, or the 15 notch. Such movement of the pawl 86 can be easily accomplished by manually pressing on the top of pawl 86, causing the stop plate 76 to deflect downward a slight amount permitting the pawl 86 to be moved out of cooperation with one notch 42 and into cooperation with another notch 42. It is to be understood that with the pawl 86 located in the 10 notch, the pin 50 would be adapted to come into contact with the next-to-theshortest-in-length recess 84. In the 15 position, the pin 50 will be caused to come into contact with that recess 84 which is located the radially greatest distance from the distributor shaft 12.

It is to be noted that located on the opposite side of the advance plate 40 are a second set of notches 44. The second set of notches 44 may be employed if the stop plate 76 is modified so as to include an additional length having another opening similar to opening 80 and another tab or pawl similar to tab or pawl 86. The second pawl would be adapted to cooperate with the notches 44. The second opening similar to opening 80 would cooperate with the pin 52. This modification is redundant. However, for safety reasons it may be employed to insure that there will be a positive stopping of the outward movement of the weights 54 and 56 at the proper advance position. Both the weights 54 and 56 should inherently move in synchronism, but this modification would insure that the weights stop in synchronism. It is not necessary that a second pawl be employed to cooperate with the notches 44 as only the single pawl 86 would be satisfactory.

What is claimed is: it

1. In combination with an ignition distributor having an input shaft and an output shaft, a drive plate fixed to said input shaft, an advance plate fixed to said output shaft, a weight assembly connected to both said drive plate and said advance plate, said weight assembly being movable upon being subjected to centrifugal force, movement of said weight assembly effecting pivotal movement of said output shaft relative to said input shaft, the improvement comprising:

a stop plate pivoted about said input shaft intermediate said advance plate and said drive plate, and adjustable to a plurality of different positions, each of said positions limiting a different amount of maximum movement of said weight assembly.

2. Apparatus as defined in claim 1 wherein:

said weight assembly includes a pin assembly fixed thereto for effecting movement of said advance plate, said pin assembly cooperating with an opening arrangement in said stop plate.

3. Apparatus as defined in claim 2 including:

notch means formed in said advance plate, and

tab means secured to said stop plate adapted to cooperate with said notch means.

4. Apparatus as defined in claim 3 wherein:

said weight assembly includes two weights,

said pin assembly includes a pin secured to each of said weights, and

said opening arrangement includes a pair of spaced apart openings,

each of said pins cooperating with one of said openings.

5. Apparatus as defined in claim 4 wherein:

said tab means includes a pair of spaced apart tabs,

and

said notch means includes dual, spaced apart sections of a plurality of notches each. 

1. In combination with an ignition distributor having an input shaft and an output shaft, a drive plate fixed to said input shaft, an advance plate fixed to said output shaft, a weight assembly connected to both said drive plate and said advance plate, said weight assembly being movable upon being subjected to centrifugal force, movement of said weight assembly effecting pivotal movement of said output shaft relative to said input shaft, the improvement comprising: a stop plate pivoted about said input shaft intermediate said advance plate and said drive plate, and adjustable to a plurality of different positions, each of said positions limiting a different amount of maximum movement of said weight assembly.
 2. Apparatus as defined in claim 1 wherein: said weight assembly includes a pin assembly fixed thereto for effecting movement of said advance plate, said pin assembly cooperating with an opening arrangement in said stop plate.
 3. Apparatus as defined in claim 2 including: notch means formed in said advance plate, and tab means secured to said stop plate adapted to cooperate with said notch means.
 4. Apparatus as defined in claim 3 wherein: said weight assembly includes two weights, said pin assembly includes a pin secured to each of said weights, and said opening arrangement includes a pair of spaced apart openings, each of said pins cooperating with one of said openings.
 5. Apparatus as defined in claim 4 wherein: said tab means includes a pair of spaced apart tabs, and said notch means includes dual, spaced apart sections of a plurality of notches each. 